Long term laboratory goals are study of the adult respiratory distress syndrome. The present focus is on inflammatory mediators and their role in the induction of lung and systemic organ injury following localized acid aspiration. The postulates to be tested are first, that acid triggers pulmonary synthesis of leukotriene B4 and thromboxane A2. Secondly, these chemoattractants by upregulating leukocyte adhesion receptors (CD18 complex) cause early local neutrophil endothelial adhesion and alveolar diapedesis. Thirdly, injury to the aspirated segment is dur to acid- protein denaturation, direct eicosanoid effects and indirect effects via neutrophils. Experiments will be conducted in rats and rabbits aspirated with 0.1 HC1 into a segmental bronchus. Leukotriene B4 and thromboxane B2 levels and neutrophil counts in bronchoalveolar lavage returns of the aspirated segment and plasma will be assayed related to oxidative activity and CD18 expression of circulating neutrophils (flow cytometry), protein content of lavage returns nad wet/dry weight ratio of the aspirated lung. Fourthly, eicosanoids may trigger interleukin-1 and tumor necrosis factor synthesis by pulmonary monocytes. These cytokines can lead to endothelial expression of adhesion molecules (ICAM-1 and ELAM-1) which may amplify and generalize the inflammatory events, leading to injury of non-aspirated lung and systemic organs. Importance of eicosanoids and cytokines as mediators will eicosanoid synthesis inhibitors; polyclonal anticytokine antibodies; monoclonal anti-CD 18 antibodies. Further, to reproduce the inflammatory sequence, authentic eicosanoids and cytokines will be lavaged or infused and the effect on leukocyte CD18 and endothelial adhesion molecules measured. Remote injury in non-aspirated lung, heart and kidney will be assessed by quantitating: leukosequestration, wet/dry weight ratio and protein level in lung lavage. Fifthly, studies will be conducted which examine the mechanisms of neutrophil-endothelial interactions. These will utilize skin abrasion preparations, isolated neutrophils and endothelial cell cultures to define: mediators of early and late neutrophil- endothelial interactions; relationship of neutrophil activation and adhesion; relationship of adhesion, diapedesis and neutrophil "desensitization" induced by inflammatory mediators. Sixthly, cytoskeletal organization of actin microfilaments in neutrophils and endothelial cells will be examined as possible determinants of activation, leukosequestratior diapedesis and permeability. Microfilaments will be quantitated by fluorescence microscopy, up and down regulated by phylloidin and cytochalasin B. Finally, the varied ability of inflammatory mediators applied to pulmonary microvessel, pulmonary artery and aortic endothelial cells to induce diapedesis and permeability will be related to phenotypic differences in endothelial structure and metabolism. The results of these studies will assist in understanding and developing strategies for the therapy of multisystem organ failure.